1. Field of the Invention
The present invention relates generally to a system and method for detecting when a negative-going pressure exists in an infusion line or container upstream of an infusion pump during administration of an infusion fluid to a patient. More specifically, the present invention relates to a system incorporating a container-side pressure sensor for sensing negative-going changes in the pressure within a fluid line, and for monitoring the container-side pressure to prevent negative-going pressure from developing due to an un-opened or blocked vent.
2. General Background and State of the Art
A common problem during infusion of therapeutic fluids into a patient occurs when the fluid to be infused is contained in burettes, bottles, or other non-flexible or partly flexible containers. When containers such as these are used as fluid reservoirs, they must be vented while the infusion is ongoing. If they are not vented, as fluid is drained from the bottle, burette, or other relatively rigid container, negative pressure is created within the container. This negative pressure may cause a reduction in flow, leading to inaccurate delivery of the therapeutic fluid.
Where an infusion pump is used to infuse the therapeutic fluid, the negative pressure building inside the container may also increase strain on the infusion pump, and may cause the pump to sound an alarm if the desired fluid infusion rate cannot be maintained. Another problem that can occur is that the negative pressure may result in air ingress into the system, especially at joints in the infusion line before the infusion line enters the infusion pump. This may result in air being entrained in the therapeutic fluid, and subsequently infused into the patient. While many infusion pumps use various types of air-in-line sensors to detect such entrained air and either halt the infusion or sound an alarm requiring attention by a care-giver before an amount of air that might injure the patient can be infused into the patient, prevention of such an occurrence is more cost-effective and efficient. Moreover, in cases where thin walled, yet rigid containers are used, the negative pressure may increase to such an extent that the thin walled containers collapse, possibly spilling their contents.
A vent is typically used in systems that will be infusing fluids from bottles, burettes, or other rigid or semi-rigid containers to prevent the build up of negative pressure as the fluid is drained from the container. However, if a care-giver forgets to open the vent or the particular drug or combination of drugs being infused wets the vent, the vent will not allow passage of air, resulting in a progressively increasing negative pressure in the container and fluid line as the pump attempts to draw fluid from the container.
What has been needed, and heretofore unavailable, is a system and method for determining when a container that requires venting to function properly is not being vented appropriately. Such a system would be able to detect the onset of negative pressure early enough so that a signal could be provided to care-givers before the infusion became inaccurate or damage was done to the pump. Moreover, such a system would be able to determine whether the intake or container-side pressure is not changing over time, indicating a stable infusion rate, or is decreasing as fluid is removed from the container, indicating lack of proper venting requiring attention by the care-giver. The present invention satisfies these and other needs.